Three months ended June 30

Six months ended June 30

Pension benefits

Other benefits

Pension benefits

Other benefits

(in thousands)

2011

2010

2011

2010

2011

2010

2011

2010

Service cost

$

8,474

$

6,772

$

1,129

$

1,131

$

17,039

$

13,382

$

2,352

$

2,219

Interest cost

14,803

14,658

2,340

2,571

29,652

29,237

4,724

5,167

Expected return on plan assets

(15,352

)

(15,353

)

(2,618

)

(2,728

)

(30,636

)

(30,677

)

(5,226

)

(5,443

)

Amortization of unrecognized transition obligation

—

(2

)

(2

)

—

(4

)

(4

)

Amortization of prior service gain

(187

)

(187

)

(312

)

(56

)

(374

)

(374

)

(539

)

(111

)

Recognized actuarial loss

4,016

1,767

37

1

8,136

3,452

55

4

Net periodic benefit cost

11,754

7,657

574

917

23,817

15,020

1,362

1,832

Impact of PUC D&Os

(556

)

2,020

1,734

1,333

(2,100

)

5,028

2,752

2,621

Net periodic benefit cost (adjusted for impact of PUC D&Os)

$

11,198

$

9,677

$

2,308

$

2,250

$

21,717

$

20,048

$

4,114

$

4,453